This invention relates to a device for accurately determining the quantative value of the real part of a complex impedance, the real part value being useful for proper impedance matching in electrical systems.
In order to achieve maximum power transfer in any system, it is necessary to determine a proper impedance match between the load and the power source. In matching, the reactive component of a complex impedance is cancelled when resonance is achieved. However, it is also desirable to determine the real part of the impedance quantitatively so that the system being matched may be properly made compatible with a source of a receiver. For example, in tuning an antenna, the impedance of an electrically short antenna has a real part which is small compared to the imaginary part as well as being small compared to the impedance (usually real) of the power source of the receiver being used. To tune such an antenna, a tuning system is required which not only cancels the reactive components of the impedance (at resonance), but also transforms the real part of the complex impedance to a value comparable with the transmitter or receiver for achieving a maximum power transfer.
The instant invention provides a device which can measure the real part of a complex impedance and can utilize the information for manual or automatic tuning to achieve a proper impedance match for maximum power transfer.
The device described herein provides for a real part impedance sensor which operates by comparing the power delivered to the load with the power dissipated in a variable resistance R when a current proportional to the main line current is passed through the resistance.